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voltage drop problem, what battery to buy?


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j.reed 
Copper - Posts: 716
Copper spacespace
Joined: January 05, 2009
Location: Arkansas, United States
Posted: December 04, 2009 at 4:09 PM / IP Logged  
michigan_tech wrote:
So what is general consensus here? I got one guy saying that my car has something to do with OnStar and all the alternators in the world won't make a different. Then another guy says that the alternator will make the world of difference.
Which is the right answer?
Also for Dominick, how do I get ahold of him? Can someone PM me his information? Which other HO alternators can I get for this thing that are direct bolt ins? I haven't had any luck and the ones I have found have very low idle output.
Here is the lone exception (EXCEPT its for the Grand Cherokee, but I think that works for Commanders too):
http://www.dcpowerinc.com/alternators/jeep/2007-2010-jeep-grand-cherokee-4-7v8-260-amp-high-output-alternator.html
Its still extremely expensive though. I'd like to hear what Iraggi has available though.
If dominic Iraggi is making them now then the onstar running through it is not going to affect it as was originally thought or they have now found the way around it. The big problem with these types of alts is the case is very small to the way it is wond. Adding wind to it was and is not easy. Hints to the price of the few that are out now. That and they are a fairly new style. Last time i checked. Mind you quite some time ago in the end of '07 beginning of '08 there was no one doing winds or after markets for these types of alts. It was also thought that the onstar and PC were regulating the voltage. You had to add alt/s for a dedicated audio charging system for anything of moderate to high end power.
Iraggi can be found quite easily on the bay. store name Iraggi Alternator And Electronics. Email is dominick@tds.net Phone 651-287-7991 he is open M-F 9am-6pm He can answer any questions about which alt you need and about the onstar. I need to call him as well the last time i did there was nothing availible for me at that time. But he does have them now.
voltage drop problem, what battery to buy? - Page 4 -- posted image.
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: December 04, 2009 at 5:52 PM / IP Logged  
michigan_tech wrote:
So what is general consensus here? I got one guy saying that my car has something to do with OnStar and all the alternators in the world won't make a different. Then another guy says that the alternator will make the world of difference.
Which is the right answer?
I thought most were in agreement.
We have discussed TWO problems:-
(1) Each time you double your power cables, you halve your cable resistance thereby halving the voltage drops. V=IR. I don't think anyone disputes that.
(2) When(ever) your alternator cannot supply enough current, your alternator voltage drops until your battery takes over. Nobody should dispute that either.
Both above in your case where about 1.5V.
Certainly IMO a 1.5V cable drop is too big and should be reduced. 0.75V may be acceptable. And that should be cheap - merely double the cabling. Is doubling again from 0.75 to 0.33V worth it? Probably not.
The alternator is a contentious issue. Many people say get a bigger battery etc. All that does is take longer to flatten.
It will NOT give you more output power when the load exceeds alternator capability.
A bigger alternator keeps the voltage high for higher loads (and usually lower RPM).
And undersized alternator means audio output drops by at least 20% - eg from 12V to 14.4V means at least a 44% increase in amplifier power output.
Keep in mind the two separate parts above. IMO neither can be disputed (except by those without reasonable understanding of them).
Another confusing issue is that changing the current available does NOT change the losses along the way - ie, the cable & distribution voltage drops. Whether you have a 100AH battery or a 10,000 AH battery will not change your 1.5V cable losses. (However, a better battery may have or hold a higher voltage at its output - ie, lower internal resistance etc. But that should be insignificant to 1.5V drops whether through cabling or undersized alternators.)
If you could reduce your cable losses by 1.5V and your alternator could supply full power, you would have at least a 60% audio output power gain (from a supply voltage POV).
There are other details - like lower alternator output at lower RPM, and resistance cause by ammeters and protection (fusing) etc. But let's KIS.
If there are any apparent contradictions, reply what they are and we'll go from there.
bigtime_077 
Member - Posts: 20
Member spacespace
Joined: December 01, 2009
Posted: December 04, 2009 at 7:32 PM / IP Logged  

Here is the way i see it.  Now maybe I am way off base here but the only thing in your vehicle that will produce electrical power is your alternator, there is nothing else not even a battery or a capacitor which are just to merely act as storage devices for the electrical power.  Now with this voltage drop you are experiencing you are not only going to eventually due damage to you car audio components but you also run the risk of damaging the electrical components of your vehicle mainly you ecu.  Your electronics in your vehicle come with a rated power that they need in order to operate properly.  As your voltage drops your amperage is going to increase because the power remains constant.  This is going to cause your electronics to get warm.  You definitely do not want to burn up your ecu because it is the "brain" of your vehicle and they are very expensive. 

With all that said before you go out and start spending hundreds of dollars on remedys lets start by doing a little self check.  First with your vehicle running and your system off check your voltage at your battery with a multimeter.  You should be producing somewhere near 14.4 volts.  If you are lower than 13.8 volts with no load on the charging system your alternators voltage regulator is shot and it will need to be replaced regardless.  Now if it comes back at near 14.4 volts and you turn your system on like maybe to half level and you are already down to say 12.5 volts I am willing to bet that the alternator is no where near big enough to handle the amp draw.  If it all checks out fine at the battery than yes it is definitely an issue of to small of wire.  Now also keep in mind that just because a manufacturer says a wire is 0 gauge and you paid $2 a foot for it you really got an 8 gauge wire with a lot of plastic coating.  Remember you are only as strong as your weakest link.  Good luck and feel free to shoot me any questions.

oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: December 05, 2009 at 5:05 AM / IP Logged  
More agreement! Bigtime is saying the same thing in an alternator-itive way.
A clarification - current goes up if voltage drops only for constant power loads - eg SMPS (switched-mode power supply) etc.
Now - subject to correction by anyone with modern or specific examples.....
ECUs generally do not have constant-power supplies since their CPUs etc only require 5V or less. A supply of 8V or above is sufficient for even the oldest linear 5V regulators. (Devices like injectors & relays may require higher voltage, but they usually run off the raw supply - ie, 8V or above.)
Hi-power audio amps use SMPS (DC-DC converters) as they have to to get several hundred Watts (eg - above 200W onto 1 Ohm speakers).
Also, Mr Mich mentioned a 1.5V voltage drop which - as i understand it - is from distribution alone - ie, from the alternator/battery via the distribution block to the amp(s). That can only be improved by decreasing distribution resistance.
If Mich's Sundowns are SMPS or equivalent, as BigTime says, with decreasing supply/battery voltage, the current increases thereby INCREASING the distribution voltage drop.
That is in addition to undersized alternator considerations.
If the vehicle's electrics could be transferred to where the amp is - including the alternator's "sense" wire, the alternator will keep that voltage at 13.8-14.4V whatever - ie, overcome the distribution drop of 1.5V etc. But apart from other consideration, unless what I, Mr Big & others are saying is understood, I would NOT attempt any such modification.
michigan_tech 
Member - Posts: 32
Member spacespace
Joined: September 16, 2008
Location: Michigan, United States
Posted: December 06, 2009 at 5:01 PM / IP Logged  
I still am confused on what you all are recommending I should do. Here are the facts once again:
1. Voltage drop of 1.5 V from the Battery to the Amp.
2. A distribution block exists at the back of the vehicle that takes in the 0 gauge from the battery and splits it into 0 and 8 guage (sub amp and 4 channel amp, respectively).
3. The big 3 all are ran at 0 gauge, and there is an additional 4 guage wire ran from the negative terminal of the battery to the grounding point in the back where the amps are also grounded.
Dominick Iraggi has a direct bolt in alternator available for me. It is pricey, but I can get 180A, 220A, 260A, 300A, or 320A. Does going too high on an alternator (Amperage wise) possibly HURT the electrical system by putting too much out?
So my question is this:
1a. Do I get the alternator?
1b. If so, does this mean I have to upgrade the battery too?
2. Do I get just a bigger battery?
3. Do I do something else with my charging wires?
Thank you
still_walkin 
Silver - Posts: 644
Silver spacespace
Joined: April 18, 2007
Location: California, United States
Posted: December 06, 2009 at 5:36 PM / IP Logged  
Well I'm not the smartest guy on here but what I would do is get the alt. The biggest your car can take as well as your pockets. But don't short change your self on this upgrade. As for a battery if its fine leave it be. Big alt small battery fast charge but on a big battery you won't have starting issues as well with a small battery and a system you might. Someone else chime in
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bigtime_077 
Member - Posts: 20
Member spacespace
Joined: December 01, 2009
Posted: December 06, 2009 at 6:48 PM / IP Logged  

Your problem with your voltage drop between your battery and your amps is due to the wiring configuration.  Your supply wire to the distribution block need to be bigger than the wire that go to your amps.  You need your wire to the distribution block to have an equal or lower resistance per foot than the combined total of the resistance of the wires that it is supplying.  Your supply wire is probably getting pretty warm to the distribution block because of this voltage drop.  Now I can relate to this because I once had a 4 gauge power wire that ran to a distribution block and then a 4 gauge to one amp and a 10 gauge to another and the supply wire got so hot that you could actually smell it burning the plastic coating off of the wire.  To remedy this I put in a 0 gauge wire from the battery to the distribution block and the problem went right away.

So all in all in your case i would either double up the wire going from your battery to the distribution block or take it out all together and put in a triple 0 gauge single wire.  Now with that said that will take care of your voltage drop their but if your one amp requires a 0 gauge wire to power it that means it likes a lot of current, way more than your stock alternator would ever dream of putting out.

So in the end the only way I see to properly solve your problem you are going to need to change your wire between the battery and amps or use a larger one and you will also need to go to a much larger alternator.  Either that or you will need to change your sub amp to a much smaller one.

Good luck michigan_tech and if you have any questions I would be more than happy to help you.

Mr. Big

michigan_tech 
Member - Posts: 32
Member spacespace
Joined: September 16, 2008
Location: Michigan, United States
Posted: December 06, 2009 at 6:53 PM / IP Logged  
As far as me needing larger than 0 gauge from the front to the back, that doesn't make sense to me. I've ran bigger amps in other cars with only 200A alternators and never had an issue. In my last vehicle, I had 0 ga from the battery to the D block and then 0 and 4 out of the block. I certainly don't think that for these two amps it causes the need for 00 or 000 gauge, I never needed those for amps that were bigger than these amps in the past.
i am an idiot 
Platinum - Posts: 13,606
Platinum spaceThis member consistently provides reliable informationspace
Joined: September 21, 2006
Location: Louisiana, United States
Posted: December 06, 2009 at 7:03 PM / IP Logged  
Have you checked to see if the voltage drop is on the power or the ground?  Connect a Wire to the battery's positive terminal  and run it to the back of the vehicle near the amplifiers.  Connect the red meter lead to that wire.  With the system playing where you experience the 1.5 volt drop, touch the black meter lead to the input terminal of the amplifier.  What is the voltage?  After getting that reading, move the black lead to the input side of the distribution block.  What is that reading?  These readings will only show the voltage drop on the power path to the amp.  Then you can move the wire to the ground connection of the battery, and do the same thing, with the meter.  First the ground terminal of the amp, then the grounding point at the chassis of the car.  Whichever (the power or the ground) shows the greater reading, needs to be dealt with. There can be nothing else connected to the wire that you ran to the battery.   
bigtime_077 
Member - Posts: 20
Member spacespace
Joined: December 01, 2009
Posted: December 06, 2009 at 7:04 PM / IP Logged  

It's not that the amps require a bigger wire to supply the power your voltage drop is occuring across your distribution block because you are changing the resistance between the wires.  If the power demand is constant and you change the resistance your voltage is going to change,  thus you end up with your voltage drop.  Just out of curiousity take a multimeter with your system on and your vehicle running and check your voltage to ground on both sides of the distribution block and see if that is where the voltage change occurs.  If so then that will prove my theory.

As always good luck and I hope to hear from you!

Mr. Big

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